Magnetic properties of isolated Re ion and Re-Re complex in ZnO studied by GGA+U approach

Highlights: • Spin states of Re ions and magnetic coupling between them is examined. • GGA+U calculations show that high spin state of isolated Re in ZnO is stable. • GGA+U calculations show that the coupling can be antiferromagnetic. • Re-doped ZnO as material that can use in magneto-optical devices. - Abstract: Magnetic properties of Re substituting for the divalent Zn ions and impurity pairs in wurtzite and zinc blende ZnO are analyzed by employing the Generalized Gradient Approximation with the +U corrections. The +U term applied to d(Zn), p(O), and d(Re) orbitals stabilizes spin polarization of Re. Re impurity introduces a defect level located in the band gap, and Re²⁺ generates the local spin 5/2 in both wurtzite and zinc blende structures. Magnetic coupling of Re-Re pairs as a function of distance between the defects, their relative orientation, and the charge state was calculated. All magnetic coupling between impurities is antiferromagnetic and due to an intermediate O atom via strong d(Re)-p(O) hybridization between Re and O states. The defect states and magnetic moments come from d(Re) with a contribution of p(O) orbitals of the O nearest neighbors of Re. The results show that the Re-doped wurtzite ZnO may be a new type of magneto-optical materials with a great promise.